Polyhalogenomethanes



United States Patent 2,716,668 POLYHALOGENOMETHANES Robert Neville Haszeldine, Cambridge, England No Drawing. Application September 15, 1953, Serial No. 380,349

Claims priority, application Great Britain November 10, 1952 1 Claim. (Cl. 260-653) This invention relates to the preparation of polyhalogenomethanes containing fluorine and at least one other halogen, some of which have been heretofore unknown.

It is known that by the heating of the silver salt of trifiuoroacetic acid with iodine, bromine, or chlorine, it is possible to obtain trifluoromethyl iodide, bromide, and chloride respectively. (R. N. Haszeldine, J. Chem. Soc. 1951, 584-587.) I

It is also known that by heating silver acetate with bromine there is obtained methyl bromide. (U. S. Patent 2,176,181 (1939) to Hunsdiecker et al.)

It has now been found that the silver salts of the much less stable halogenofluoroacetic acids either fully substituted or containing unsubstituted hydrogen, may be heated with elemental iodine, bromine, or chlorine to produce thev analogous substituted polyhalogenomethanes, the term halogeno in the name halogeno-fluoroacetic acid being used to denote a halogen other than fluorine.

In carrying out the process of the invention, the halogenofiuoroacetic acid containing at least one fluorine atom on the alpha carbon atom is converted to its silver salt, and a mixture of this salt and the selected halogen (chlorine, bromine, or iodine), preferably used in stoichiometric excess, is heated to decarboxylation temperature, generally in the range to +300 C., at a pressure in the range of about 0.001 atmosphere to about atmospheres for a period of time in the range of about 0.1 hour to about 10 hours. A fluorohalogenomethane corresponding to the alpha carbon atom of the acetic acid with its substituents, and the selected halogen added, is thereby produced. The reaction may be represented generally thus:

By the process of the invention a number of halogenomethanes not previously known have been prepared.

preparation of this class of compounds but are not intended to limit the invention.

Example I Example 1 was repeated using a 5% stoichiometric excess of bromine instead of chlorine to produce a 62% yield of-CHzFBr; B. P. 17.5 C.

Example 3 Silver monofluoroacetate a stoichiometric excess of iodine and heated to -260 C. with continuous removal of the products under vacuum into a trap cooled in liquid air, to give a 55% yield of CHzFI; B. P. 52-53 C.

Example 4 (3.1 parts) was heated as a 73% yield of CHFClz;

Silver chlorofiuoroacetate in Example 1 above to give Example 5 Silver chlorofluoroacetate (3.1 parts) was heated as in Example 2 above to give a 67% yield of CHFBrCl; B. P. 36.5 C.

- Example 6 Silver chlorofiuoroacetate (4.2 parts) was heated as in' Example 3 above to give a 35% yield of CHClFI; B. P. 35 C./150 mm. or Ca. 76 C./760 mm.

Example 7 Silver bromofluoroacetate (3.3 parts) was heated as in Example 1 above, except that a temperature of 40 C.

was employed, to give a 67% yield of CHFBrCl.

Example 8 Silver bromofluoroacetate (3.3 parts) was heated as in Example 2 above, except that a temperature of 100 C. was employed, to give a 64% yield of CHBrzF; B. P. 64.5 C.

Example 9 Example 10 Silver fluoroiodoacetate was heated with a 300% stoichiometric excess of iodine and at a pressure of 1 mm.

as in Example 9 above to give an 18% B. P. 50 C./50mm.

yield of CHFIz;

Example 11 (3.2 parts) was heated at 50 C. stoichiometric excess of chlorine in a steel yield of CHCIF2; B. P. -41 C.

Example 12 1 Example 13 Silver difiuoroacetate 3.1 parts) was heated in an autoclave with a 5% stoichiometric excess of bromine to give Silver difluoroacetate with a 10% autoclave to give a 91% a 93 yield of CHBrFz.

(8.2 parts) was mixed With- Example 14 Silver difiuoroaeetate (10.1 parts) was mixed with a 50% stoichiometric excess of iodine and heated at a temperature of about 150 C. to give a 93% yield of CHFzI; B.'P. 20.5 C.

Example 15 Silver bromochlorofiuoroacetate (5 parts) was heated with bromine as in Example 2 above to give a 71% yield of CBrzClF; B. P. 79.580.5 C.

Example 16 Silver bromochlorofluoroacetate heated with chlorine according to the procedure of Example 2 above gave a 63% yield of CBrClzF.

Example 17 Silver bromodifiuoroacetate was heated with a stoichiometric excess of bromine as in Example 2 above to give an 81% yield of CBrzFz; B. P. 25 C.

Example 18 heated with yield of Silver chlorodifluoroacetate (5 parts) was chlorine as in Example 1 above to give an 88% CClzFz; B. P. -29.5 C.

Example 19 Silver chlorodifluoroacetate (5 parts) was heated with bromine as in Example 2 above to give a 91% yield of CBrClFz; B. P. 4 C.

Example 20 Silver chlorodifiuoroacetate (5 parts) was heated with a stoichiometric excess of iodine as in Example 3 above and at a pressure of 10 mm. of Hg. to give a 78% yield of CC1F2I', B. P. 33 C.

Example 21 Silver dichlorofiuoroacetate (3 parts) was heated with bromine as in Example 2 above to give CBrClzF; B. P. 51-52 C., in 58% yield.

Example 22 Substitution of chlorine for bromine in Example 21 above gave CClsF in 63% yield, B. P. 23-24 C.

Example 23 References Cited in the file of this patent UNZTED STATES PATENTS La Zerte et a1 Aug. 4, 1953 Conley M May 18, 1954 OTHER REFERENCES Stepanov Compte Rendus, (Doklady) U. S. S. R. 45, No. 2. pages 56 and 57 (1944).

Delvvalle et al., Compte Rendus 214, pages 828 to 830 (1944).

Haupschein et al., I. A. C. S. 73, pages 2461 to 2463 (iune1951).

Haupschein et al., I. A. C. S. 74, pages 1347 to 1350 (March 5,1952).

fNature, volume 166, pages 192-193 (July 29, 1950). 

